NEW ORLEANS - A negative FDG-PET scan is highly useful for excluding distant metastases in patients with pre-resection esophageal cancer, according to a poster presentation at the 2003 Society of Nuclear Medicine meeting.
Esophageal cancer is just one of the many health hazards that heavy alcohol drinkers and/or smokers face, and its incidence is rising in the United States. The disease has a five-year survival rate or less than 5%, a 90% death rate, and frequently spreads to almost any other part of the body including the lymph nodes, the liver, and the lungs, explained Dr. Izzat Chalabi and colleagues from the University of Maryland Medical Systems in Baltimore.
Conventional staging for this type of cancer is done with ultrasound and CT scanning. The latter is adept at identifying tumors and lymph nodes based on anatomical size. Endoscopic esophageal sonography allows for direct visualization of the tumor, but it is an invasive procedure, the authors wrote.
"PET is excellent for its ability to detect liver, lung, and skeletal metastasis," they explained. "It also has proven to be useful in differentiating recurrent disease from scar tissue."
For the retrospective study conducted between October 1999 and July 2002, 55 esophageal cancer patients (average age 62.7) underwent FDG-PET imaging as well as diagnostic evaluations with CT and endoscopic ultrasound (EUS) with or without fine-needle biopsy of the lymph nodes. The workup and tumor classification was based on CT scans of the chest and abdomen. Pathology results from the tumor, nodal, and distant metastases were considered the gold standard. Tissue confirmation of nodal metastases was done with pre-treatment thoracoscopic
Of the 55 primary tumors, 72% were adenocarcinoma and 28% were squamous cell carcinoma. The majority of squamous cell tumors were found in the upper and middle esophagus, while adenoncarcinomas were found in the lower section. The positive predictive value (PPV) and the negative predictive value (NPV) were determined by the ability of the various modalities to correctly identify nodal and distant metastases.
According to the results, 60% of the adenoncarcinomas were found to have lymph node or distant site metastases. The same was true for 40% of the squamous cell carcinomas. The sensitivity of FDG-PET for detecting the primary esophageal tumor site was 91.9%. In comparison, the sensitivity for CT was 87.5% and 100% for EUS.
For detecting nodal disease, the group reported a sensitivity of 50% for PET. The specificity came in at 87%, the PPV at 85%, and the NPV at 55.6%. For CT, the sensitivity was 27.3%, the specificity was 91.3%, the PPV was 81.8%, and the NPV was 46.7%.
For the detection of distant metastases, PET’s sensitivity was 88.8%, the specificity was 89.2%, the PPV was 80%, and the NPV was 94.3%. For CT, sensitivity was 33%, specificity was 85%, PPV was 45%, and NPV was 77%.
Two of 55 cases were false-negative, and 4 of 55 false-positive on the PET exams. The latter was attributed to an increased uptake localized in the liver. The mean standard uptake values (SUV) by tumor stage was 2.6 for T1 stage tumors, 8.0 for T2 stage, 8.31 for T3, and 13.6 for stage T4.
The authors concluded that PET was the most accurate test for assessing distant metastatic lesions (89% accuracy) versus 71% for CT. PET results could also guide additional pre-treatment intervention for esophageal cancer, they wrote. By way of example, the authors cited the case of a 76-year-old female who presented on CT and PET with retrocardiac and paraesophageal masses. The PET scan a year after treatment showed resolution of the chest disease, but depicted a large mass in right side of the neck, which was not seen on the corresponding CT exam.
By Shalmali PalAuntMinnie.com staff writer
June 26, 2003
Related Reading
Chemoradiotherapy of long-term benefit in inoperable esophageal cancer, February 7, 2002
New technique tracks spread of esophageal cancer, September 7, 2001
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